Method of recording charged particles



United States Patent 3,353,185 METHOD OF RECORDING CHARGED PARTICLES Heinz F. Nitka, Binghamton, N.Y., asssignor to General Aniline & Film Corporation, New York, N.Y., a corporation of Delaware No Drawing. Filed Apr. 2, 1964, Ser. No. 356,932 4 Claims. (Cl. 346-1) The present invention relates to a radiation exposure method of successive image recording on different areas of the same photosensitive element while employing elec tromagnetic energy of invisible type, such as that obtained in the electron beam recording process.

It is known that certain photographic recording processes can be carried out by the use of print-out types of reproductive material. The term print-out refers to the process whereby images are produced on a photosensitive material by exposure to radiation without chemical development. A latent image is first formed which is rendered visible by further actinic radiation. The latent image, obtained after a simple exposure to relatively intense radiation, is developed directly into a reasonably permanent image by exposure to further radiation of lower intensity. Print-out materials of this kind are frequently used, for example, for recording the traces of oscillograph recording apparatus and the like.

In a typical case, an invisible latent image is first obtained by very short time exposure to the intense recording beam of the oscillograph and thereafter the visible image is obtained by developing the latent image by a simple exposure to white light, This additional or second exposure is commonly known as latensification. Latensification includes re-exposing the area upon which the initial image was formed as well as exposing, for the first time, the surrounding background areas.

One of the most characteristic features of print-out emulsions is their capacity to be developed solely by exposure to white light. The actual trace exposure is followed, usually quite promptly, by the overall post-exposure, as mentioned above. This fulfills two different functions. The post-exposure to light of lesser intensity, as normally employed, develops the trace image, causing addition of reduced silver to the latent image. At the same time, it stabilizes the unexposed areas against rapid print-out under ordinary light conditions as long as they are kept indoors or illuminated only at low intensity, as in storage in typical business ofiices. Hence, an acceptably low background density is retained and the trace image, as developed by the second exposure to light, is clearly distinguishable and can be retained for some time. However, ,the sensitivity of the paper to a further trace exposure," for example on the oscilloscope, is also very heavily reduced after the light post-exposure. While the paper, with its developed image, can be kept in storage under ordinary conditions of light for an extended period of time, it cannot be re-used with the oscillograph for another recording.

A typical photographic emulsion of the print-out type may be composed of a major proportion of silver bromide, with small proportions of silver iodide combined with a small proportion of a lead, stannic or cadmium salt, preferably a lead salt. The lead salt is a lead halide such as lead bromide, chloride or iodide. These materials are all combined in a suitable colloidal carrier or binder, such as gelatin or methyl cellulose. If desired, a suitable chemically treated starch such as the hydroxyalkyl starch mentioned in U.S.P. 3,047,392 may be employed as the emulsion carrier,

According to the present invention, photographic materials of the same general types as described above may be employed advantageously for the successive recording of visible images on different areas of the same material 3,353,185 Patented Nov. 14, 1967 by an invisible electromagnetic energy such as that obtainable in a charged particle recording apparatus. In such accelerator apparatus as is well known in the art, electrons or ions are submitted in an electric field to voltages capable of accelerating these charged particles. An electric field having a voltage between 2 and kilovolts is preferred for the acceleration of electrons. The accelerated ions are provided by elements having an atomic number between 1 and 18, thus including the ions of elements beginning with hydrogen and ending with argon. So accelerated, the electrons, ions or even slow neutrons can be recorded on the recording media described above. Charged particles and their action on conventional photographic emulsions are described in chapter 8 of Mees book, The Theory of the Photographic Process, revised edition, 1959.

After the electron or ion beam exposure, the first latent image produced by the beam is developed by post-exposure to visible light of moderate intensity in the same manner as in the case of oscilloscope exposure described above. A suitable intensity for such development or latensification is that obtained by the use of a 15 watt white fluorescent lamp at a distance of 12 inches from the paper. The preferred exposure time is from about 5 to about 60 seconds. This post-exposure adequately develops the latent image produced by the electron or ion beam. However, unlike the case for oscilloscope exposure, this postexposure does not substantially desensitize the paper in the unexposed areas so far as a subsequent exposure to an electron or ion beam is concerned. The result is that a sheet, on which a trace has been made by an electron or ion beam, which has been developed by subsequent exposure to relatively subdued light, may be re-used for further electron or ion beam recordings. The original electron or ion beam image is not erasable but a new recording by electron or ion beam may be placed on a difierent area of the same sheet. This recording is followed by the latensifying post-exposure as described above. This makes it possible to re-use each sheet several times for electron or ion beam recording and subsequent latensification. If desired, comparative records, in a sequence, may thus be made directly on a single sheet.

Hence, the advantages obtainable by the procedure of this invention are considerable, Relatively inexpensive sheet material of dry type can be exposed and re-exposed for the recording of several images at different times without any chemical treatment whatsoever. The recording media, when used in electron or ion beam recording, have special utility, not only because of their being re-usable but because of the fact that comparative traces can be made in sequence or in series on different areas of the same sheet. This is highly advantageous, particularly in research work.

A typical emulsion suitable for application to paper or film of the print-out type may comprise approximately the following formula:

Grams Silver bromide 100 Silver iodide O.5-5 Lead chloride 0.1-5 An inert binder of gelatin or cellulose 5075 Enough water to make a suitable emulsion consistency.

The proportions of ingredients indicated above may be varied somewhat within the general limits stated. A preferred composition comprises 100 grams of silver bromide, 1 to 3 grams of silver iodide with l to 2 grams of lead chloride, lead iodide or lead acetate.

Various modifications may be made in the process and it is intended to cover such as would occur readily to those skilled in the art as broadly as possible, within the scope of the following claims and as far as the prior art properly permits.

What is claimed is:

1. The method of recording intelligence, which comprises the steps of applying to a sheet support an emulsion which comprises silver bromide and silver iodide, and a lead salt in a colloidal carrier, exposing an area of said emulsion-bearing sheet to a beam of charged particles which is accelerated in an electric field of a Wide voltage range to form a latent image developing said image by overall post-exposure to visible light, subsequently re-exposing a different area of the light exposed emulsion to an electron or ion beam to produce a second, independent latent image and developing the latter image by post-exposure to visible light.

2. The process as defined in claim 1 wherein the postexposure is effected by a white light source at a distance of 12 inches from the emulsion.

5 voltage range of 2 to 100 kilovolts.

References Cited UNITED STATES PATENTS 10 3,047,392 7/1962 Scott -3 '9645.2X 3,152,902 10/1964 Jacobs 9645.2X 3,281,858 10/1966 Schwertz 34674 15 BERNARD KONICK, Primary Exwminer.

L. I SCHROEDER, Assistant Examiner. 

1. THE METHOD OF RECORDING INTELLIGENCE, WHICH COMPRISES THE STEPS OF APPLYING TO A SHEET SUPPORT AN EMULSION WHICH COMPRISES SILVER BROMIDE AND SILVER IODIDE, AND A LEAD SALT IN A COLLOIDAL CARRIER; EXPOSING AN AREA OF SAID EMULSION-BEARING SHEET TO A BEAM OF CHARGED PARTICLES WHICH IS ACCELERATED IN AN ELECTRIC FIELD OF A WIDE VOLTAGE RANGE TO FORM A LATENT IMAGE DEVELOPING SAID IMAGE BY OVERALL POST-EXPOSURE TO VISIBLE LIGHT, SUBSEQUENTLY RE-EXPOSING A DIFFERENT AREA OF THE LIGHT EXPOSED EMULSION TO AN ELECTRON OR ION BEAM TO PRODUCE A SECOND, INDEPENDENT LATENT IMAGE AND DEVELOPING THE LATTER IMAGE BY POST-EXPOSURE TO VISIBLE LIGHT. 